In this research project we aim to use our special resources and methodological expertise to identify and characterize the molecular defects in two multiple malformation syndromes leading to stillbirth or death during the first days of life. Using genome wide searches we have positioned these loci and are very close to the final identification of the causative genes. Since these two severe malformation syndromes share several hallmark symptoms, it is probably that the molecular defect in them will guide us to partially interacting metabolic pathways, which provide novel insights into early normal fetal development more generally. However, the syndromes show also deviation in their tissue specificity and the molecular defects might guide to the tissue specific components during organogenesis. Since both syndromes represent early developmental disturbance, we predict that the causative genes will have homologies in low species and aim to use Drosophila as the primary experimental organism to dissect the disturbed metabolic pathways and interactive genes. In the case of the Meckel syndrome on chromosome 17 we have restricted the critical DNA region to 1272 kb and most of this region is sequenced. We have further identified 20 EST contigs or novel transcripts on this region, one novel transcript having a homologous gene on the second Meckel region on chromosome 11 and being a highly interesting candidate. Via expression analyses and efficient search of DNA variants in patients samples we will identify the Meckel gene in near future. To pursue the components of the disturbed metabolic pathway resulting in malformations in the Meckel syndrome future. To pursue the components of the disturbed metabolic pathway resulting in malformations in the Meckel syndrome we will be using: a) "Cybercloning" of potential genes with homology, or known, or predicted interaction on the region of chromosome 11q 13 containing the second Meckel syndrome gene. b) The Drosophila system as an experimental model to identify genes and gene products interacting with a Drosophila gene, homologous to human Meckel gene(s). In the case of the hydroethalus syndrome the critical DNA region is 220 kb. This region is currently being sequenced in the Sanger Center and so far we have identified 15 EST contigs or novel transcripts on this region and we are currently analyzing the tissue expression and sequence of this genes in patients and controls to identify the causative gene. Again we plan to pursue the consequences and involved biochemical pathways in the Drosophila system. For both diseases we will initially search for deficiency lines and P- element lethals of Drosophila to be able to analyze the consequences of the identified mutation mutations in the Drosophila model. If no homologies are found in the fly genome, as an alternative strategy we are prepared to produce the knock out mouse using the cre-lox strategy. The expertise of our collaborators, Dr. Lawrence Zipursky and Dr. York Marahrens in these technologies will guarantee our skills in these strategies.